Explain whyWater can reach up to endodermis through apoplast?



Explain why?
(i) Water can reach up to endodermis through apoplast but it moves through the endodermis by symplast.
(ii) Primary xylem in root is exarch and in stem it is endarch.


(i) The endodermal cells are somewhat different from other living cells of root in having a conspicuous, waxy thickening, the casparian strip, in their cell walls. The wax-like
substance, cells suberin, present in the casparian strips blocks the movement of water and minerals from one side to the other via cell wall route. Thus, water moves through the endodermis via cell sap by symplast.
(ii) Primary xylem is exarch in roots to facilitate maximum inward movement of water from the cortex. Whereas it is endarch in stem to minimise the loss through cortex and epidermis